GB2303693A

GB2303693A - Gas treatment with liquid spray

Info

Publication number: GB2303693A
Application number: GB9515388A
Authority: GB
Inventors: Maurice Edward George Maton
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-07-27
Filing date: 1995-07-27
Publication date: 1997-02-26
Also published as: GB9515388D0; WO1997004854A1; AU6620996A

Abstract

Gas treatment apparatus comprises a generally cylindrical chamber 1 through which the gas is caused to flow. The chamber 1 has a gas inlet pipe 2 projecting into the chamber from which the gas flows towards a gas outlet 3. A pair of water pipes 4 conduct water coolant to opposite sides of the chamber 1 where it is sprayed into the gas flow through nozzles 5 directed at least partially towards the gas outlet 3. The water cools the gas, condenses hydrocarbon impurities such as tars and oils, and collects solid particles from the gas. A mixture of the water, hydrocarbon condensate and solid particles falls to the bottom of the chamber 1 and down to a drain 6 at the outlet end 3' of the chamber. Each nozzle 5 produces a spray in the form of a thin, curtain-like water film which extends to the opposite side of the chamber.

Description

GAS TREATMENT APPARATUS This invention relates to gas treatment apparatus. One application of the invention is for cooling gas and for removing solid particles and other impurities therefrom.

An example of another application of the invention uses a stream of hot gas for heating water.

In many cases the gas under treatment will be air.

According to a first aspect of the invention, gas treatment apparatus comprises a chamber through which gas is caused to flow between an inlet and outlet thereof, and nozzle means for introducing liquid into the chamber for treating the gas, the nozzle means being adapted to produce a plurality of sprays in the form of sheets of the liquid.

Preferably each sheet comprises a thin, curtain-like film forming an obstacle in the path of the gas. The films may be distorted by the gas flow when this is introduced into the chamber.

The nozzle means conveniently comprises a plurality of spray nozzles, each nozzle producing a said spray.

The spray nozzles are preferably disposed In arrays on opposite sides of the chamber, and most preferably, on passing along the chamber from the inlet to the outlet the gas encounters a series of sprays coming alternately from opposite sides of the chamber.

An outlet from the chamber for the gas is conveniently provided in an upper side wall portion of one end of the chamber, an outlet from the chamber for liquid from the nozzles being conveniently provided in a lower side wall portion, preferably at the same end of the chamber.

Forms of gas treatment apparatus are known in which a stream of gas is introduced into one end of a chamber, and water for treating the gas is sprayed downwardly into the stream of gas from spray nozzles mounted near the upper wall of the chamber, the treated gas then being taken off from the other end of the chamber, and the water from the nozzles being collected from the bottom of the chamber.

However, the form of the sprays disclosed in connection with the first aspect of the invention, as well as the preferred arrangements of the sprays, conveniently provides a high level of exposure of the gas to the liquid being used for treating the gas, enabling a compact and efficient form of gas treatment apparatus to be constructed.

The invention may be used purely for removing impurities from a gas including, for example, solid particles and condensible substances which are trapped by the liquid sprays. Additionally, or alternatively, the invention may use the liquid to change the temperature of the gas.

Where the invention is applied for heating water, the water is the liquid introduced into the chamber, and this is heated by the gas being hot gas. A convenient supply of hot gas is exhaust gas from suitable fuel burning apparatus.

In attempting to use existing forms of commercial apparatus for cooling gas rapidly from temperatures above about 500 -800 C to near room temperature using water sprays, it has been found that the rapid cooling can result in shock waves which cause an undesirable, pulsating flow of gas.

The applicants have realised that a steady suction effect can be obtained by angling the spray nozzles slightly towards the gas outlet from the chamber, so reducing any tendency to produce shock waves.

According to a second aspect of the invention, gas treatment apparatus comprises a chamber through which gas is caused to flow between an inlet and outlet thereof, and nozzle means for introducing liquid into the chamber for treating the gas, the nozzle means being directed at least partially towards said outlet so as to be angled at less than 90" to the general direction of gas flow between said inlet and said outlet.

In a preferred form of gas treatment apparatus according to the second aspect of the invention, the nozzle means is also adapted to produce a plurality of sprays in the form of sheets of the liquid, in accordance with the first aspect of the invention.

Preferably sald sprays in the form of sheets of the liquid are directed by the nozzles at an angle of substantially 45" to 850 to the longitudinal axis of the chamber. The angle is most preferably substantially 80".

The spray nozzles are desirably disposed in arrays on opposite sides of the chamber such that, on passing along the chamber from the inlet to the outlet, the gas encounters a series of sprays coming alternately from opposite sides of the chamber. Conveniently the angling and spacing of each of the nozzles is such that each spray in the series is directed at the base of the next spray In the series so that, at least prior to introduction of the gas flow into the chamber, the sprays do not intersect.

Where the invention is used with pyrolysis apparatus for cooling the gas produced by the pyrolysis apparatus and for removing condensate and solid particles from the gas, hydrocarbon condensate is desirably returned to the pyrolysis apparatus for further pyrolysls treatment.

Where the gas carries solid or condensible material, as in the case of use with pyrolysis apparatus, the inlet to the gas treatment apparatus may desirably be provided with scraping means for removing any material deposited in the inlet.

However, the inlet most preferably comprises a pipe projecting into at least the first spray of a series of the liquid sprays since this has been found to reduce any tendency for the inlet to foul with the material carried by the gas.

The chamber of the apparatus of the invention is preferably of elongate form, with the inlet for the gas located towards one end of the chamber, and the outlet for the gas towards the other end of the chamber. The chamber is conveniently of cylindrical form, and the inlet end is preferably higher than the outlet end.

For this reason, the longitudinal axis of the chamber is typically inclined, the angle of inclination preferably being substantially 50 to 15 to the horizontal, but most preferably substantially 10 to the horizontal.

By way of example only, a specific embodiment of the apparatus of the invention will now be described with reference to the accompanying drawings, in which: Figure l is a diagrammatic side view of the apparatus, Figure 2 is a diagrammatic section view along on section line 2-2 of Figure 1, Figure 3 is a diagrammatic end view of the apparatus, viewed from the lower end of the chamber, and Figure 4 is a diagrammatic cross-section view on section line 4-4 of Figure 1, showing the spray configuration.

The applicants international patent application No. PCTIGB 93/01213 (WO 93/25848) describes apparatus for pyrolysis of waste materials such as domestic rubbish, which produces a stream of hot, combustible gas bearing solid particles such as particles of carbon, and oils, tars and other impurities.

The specific embodiment is a gas cooling apparatus using water sprays for cooling gas produced from such pyrolysis apparatus from around 500"-800"C to about 25"C and for condensing and removing liquid substances from the gas together with solid particles and various other impurities.

As shown in the accompanying drawings, gas-cooling apparatus according to the invention comprises a generally cylindrical chamber 1 through which the gas is caused to flow. The chamber 1 has an inlet for the gas which comprises an inlet pipe 2 projecting into the chamber (Figures 1 and 2) from which the gas flows towards an outlet 3 for the gas at outlet end 3 of the chamber 1. A partition 20 forms one end wall of chamber 1, whilst the opposite end wall is indicated by reference 30. The chamber 1 is supported by a leg 11.

A pair of water pipes 4 conduct water coolant to opposite sides of the chamber 1 where it is sprayed into the gas flow through nozzles 5 directed at least partially towards the gas outlet 3. The water not only cools the gas, but also condenses hydrocarbon impurities such as tars and oils, and collects solid particles from the gas A mixture of the water, hydrocarbon condensate and solid particles therefore falls to the bottom side of the chamber 1 and then, due to the axis 7 of the chamber being inclined to the horizontal at about 10 , the mixture flows down to a drain 6 at the outlet end 3 of the chamber, from which it leaves the chamber.

The hydrocarbon condensate may then be separated from the mixture and returned to the pyrolysis apparatus, for further pyrolysis treatment.

Due to the nozzle shape, each nozzle 5 produces a spray in the form of a thin, curtain-like water film which extends to the opposite side of the chamber. The films are not directed perpendicularly to the cylinder axis, but are angled slightly towards the outlet end 3 of the chamber, so as to intersect the axis 7 at about 80".

As viewed in Figure 3, dotted line 8 delimits the rear of a water film coming from a nozzle 5 on the left hand side of the chamber l, whereas dotted line 9 delimits the rear of a water film coming from a nozzle 5 on the right hand side of the chamber 1.

The angle and spacing of the nozzles is such that the film produced by each nozzle impinges near the base of the next nozzle in the series on the opposite side, at least prior to introduction of the gas flow into the chamber. The chamber is thus partitioned by a series of water films passing in a zig-zag formation from the gas inlet 2 to the gas outlet 3.

Although the films are disrupted by the flow of gas, the angled configuration of the films gives a steady suction effect as the gas is cooled and promotes flow of the gas from inlet pipe 2 to outlet 3 without pulsating.

The inlet is in the form of a pipe 2, the end of which projects into the first of the series of sprays, since this arrangement has been found to reduce any tendency for the inlet to foul with impurities carried by the gas. An automatic scraping device (not shown) can also be provided to remove any impurities deposited at the inlet.

A demister in the form of a mesh may cover the gas outlet 3 to remove spray and other remaining particles from the gas.

In a preferred embodiment, there is a series of 12 nozzles on each side of the chamber, although in the drawings only six are shown on each side. Suitable nozzles have been found to be gas burner fan nozzles produced by Bray Burners of Education Road, Leeds. The nozzles have part number 23A1906 and part reference CAT 4277.

Claims

1. Gas treatment apparatus comprising a chamber through which gas is caused to flow between an inlet and outlet thereof, and nozzle means for introducing liquid into the chamber for treating the gas, the nozzle means being adapted to produce a plurality of sprays In the form of sheets of the liquid.

2. Apparatus as claimed in claim 1, in which the nozzle means ls directed at least partially towards said outlet so as to be angled at less than 90" to the general direction of gas flow between said inlet and said outlet.

3. Apparatus as claimed in claim 1 or claim 2, in which the nozzle means comprises a plurality of spray nozzles, the chamber having a longitudinal axis, and the spray nozzles directing the sprays at an angle of substantially 45" to 85" to said axis.

4. Apparatus as claimed in claim 3, in which the spray nozzles are disposed in arrays on opposite sides of the chamber, and most preferably, on passing along the chamber from the inlet to the outlet the gas encounters a series of said sprays coming alternately from opposite sides of the chamber.

5. Apparatus as claimed in claim 4, in which the inlet comprises a pipe projecting into at least the first spray of the series of said sprays.

6. Apparatus as claimed in any one of the preceding claims for use in heating water, the water being the liquid introduced into the chamber, and heating of the water resulting from the temperature of the gas being higher than that of the water.

7. Gas treatment apparatus substantially as hereinbefore described with reference to the accompanying drawings.